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Putented Apr. 9, 1946 2,398,001 UNITED STATES PATENT oer-‘Ice 2,398,001 INSULATING MATERIAL Cli?ord 1. Barley and Mervin E. Martin, Cumber land, Md., assignors to Celanese Corporation of America, a corporation of Delaware No Drawing. Application June 1-1, 1942, Serial No. 446,614 (Cl. 106-122) from the body of the shaped cellulose ester leav This invention relates to insulating material, ' 6 Claims. and relates more particularly to insulating ma terials having a basis of regenerated cellulose. .The present application is a continuation in part of our copending application S. No. 398,547, ing behind a cellular mass or structure. By yet another method, a product having pores of substantially uniform size may be obtained without the necessity of incorporating inorganic matter therein. In accordance with the latter ?led on June 18, 1941. process. there is added to the cellulose ester in An object of our invention is the production of ?nely divided form, a volatile liquid or mixture of heat insulation materials from materials having liquids having, in the vapor state, at least a sol a basis of regenerated cellulose of a cellular structure. 10 vent, swelling or softening action thereon, and the mixture is subjected to the action of elevated Another object of our invention is the produc temperature and pressure in a closed chamber. tion of heat insulation material of low density Examples of the liquids or liquid mixtures which which may be easily fabricated in any desired shape. ‘ Still another object of our invention is the pro duction of heat insulation material which is rela may be employed are acetone, ethyl alcohol, ethyl alcohol and benzol, water, chloroform, ethylene dichloride, acetone and ethyl or methyl alcohol, tively inexpensive, highly'reslstant to the action ethylene dichloride, and ethyl or methyl alcohol, of organisms such as fungi, and which has a low methyl chloride and ethyl or methyl alcohol, bu speci?c thermal conductivity. tanol, diacetone alcohol, and gasoline hydrocar Other objects of our invention will appear from 20 bons, as well as mixtures of organic liquids with the following detailed description. various amounts of water. While all these liquids Materials having a cellular structure have long been employed for insulation purposes. The ma are suitable, acetone, butanol, ethyl alcohol, and is that the pore size is variable and irregular, and there is di?iculty in ensuring that all of gas generating solid is decomposed. In accordance temperatures. mixtures of these liquids with water or benzol, are preferably employed. The conditions of ele terial most commonly employed has been cork, which has usually been employed in the form of 25 vated temperature and pressure are maintained until the cellulose ester is at least partially con boards of varying thicknesses. The cork board verted and the pressure is then suddenly released. is prepared by compressing particles of ?nely The sudden release of the pressure while the divided cork, with or without some binding ma treated material is at an elevated temperature terial, under sufficient pressure to cause the par ticles to adhere. In place of cork, it has been 30 allows the liquid absorbed therein to vaporize with extreme rapidity and the cellulose ester is proposed to prepare insulating materials from expanded to a strong, ?lm, cellular material of other materials having a cellular structure, such low density and even texture suitable for many as, for example, those prepared from thermoplas purposes. Among the uses of the product of this tic materials having a basis of a cellulose ester. Such cellular materials have been prepared 35 process is the employment of the expanded ma , terial for thermal insulating processes. When in several ways. According to one method the cel forming a board from the comminuted material lulose ester is dissolved in a solvent to produce a made in accordance with this prior process by viscous solution and there is incorporated therein subjecting the latter to pressure in the presence a solid which is capable of being decomposed by heat or chemical treatment to yield a gas. After 40 of a binding agent, the necessary pressure often destroys the cellular character of the material. the solution has been set, or substantially set, the Such change substantially reduces the thermal mass is then treated so as to decompose the gas e?iciency of the material. Also due to the ther generating solid and the generation of the gas moplastic nature of the material its scope of therefrom causes the formation of hollow spaces throughout the mass, resulting in a porous or cel 45 usefulness is circumscribed because of the fact that it is subject to some deformation at elevated lular structure. The disadvantage of this process We have now discovered that insulating mate rial of high thermal efficiency having certain ad with another method, a solution of a cellulose 50 vantages over the insulating material of the prior processes may be prepared by uniting commi ester in a volatile solvent is prepared and soluble nuted, regenerated cellulose materials prepared inorganic salts of appreciable particle size are by the saponificiation in whole or in part of dis mixed therewith. After the solution has been crete particles of expanded cellulose ester mate suitably shaped and then set by removal of the solvent, the soluble salts are extracted with water 55 rials. In accordance with our invention, expand 2 2,398,001 ed cellular material havinga basis of a cellulose ester obtained for example, by any of the proc esses outlined above, is reduced to a comminuted form and the resulting cellular material of small particle size is subjected toythe action of a suit The saponi?cation and washing may comprise .a batch process or it may comprise a continuous process, the discrete cellular particles of the cel lulose ester being carried through the saponify ing bath at any desired speed as by a screw con able saponifying bath. ,The regenerated cellu veyor or the equivalent, followed by washing in lose particles obtained in this manner retain the a similar manner. After washing, the regener ated cellulose particles may be dried. cellular structure originally present. When such The size of the discrete particles employed in particles are set in the desired form by means of a suitable binding agent, the resulting product 10 the production of insulating material in accord is a material of low density possessing a hi h ance with our invention has a de?nite bearing thermal insulating efficiency, as indicated by its on the properties of the ?nal product. If the par ticle size too closely approaches the size of the low heat transfer coefficient. Not only may the cellular, regenerated cellulose particles be set in individual cells present in the structure, the cel any desired shape, in accordance with our novel 15 lular character will largely be destroyed and the effect of temperature and pressure will cause the ' process, but/the product thus obtained may be product to be substantially solid in character cut, sawed, “nailed, etc. and may be employed rather than cellular, since the material being wherever insulation material is necessary or de subjected to treatment will be more in the na sirable. In lieu of binding the particles with a suitable binding agent, the cellular particles may 20 ture of a powder substantially devoid of cells. For this reason the average particle size should also be employed for insulating purposes .in a be at least larger than the average size of the loose form. When employed in this manner, the cells so that the cellular nature of the material cellular particles may be placed in air spaces sur may be retained. The size of the particles may, rounding the chamber to be insulated and in this way an improved insulating effect may be ob tained. 25 of course, be considerably larger than this. To enable the regenerated cellulose particles Conveniently, the saponi?cation of the cellular materials may be carried out by treatment with organic saponifying agents such as for example, to be formed'into a ?rm mass, the particles are or other organic base, or it may be carried out with inorganic agents, such as for example, so-v a derivative of cellulose, such as cellulose acetate, dium hydroxide, potassium hydroxide, sodium silicate, ammonium hydroxide, sodium carbonate in the form of a solution, or applied as a powder an aqueous or an alcoholic solution of the sa ticles of regenerated cellulose, the binding agent held together by a suitable binding agent. Thev binding agent may be a glue, such as casein glue, methyl amine, ethylene diamine, triethanolamine 30 animal glue or vegetable glue. It may also be or a resin or gum, applied with a volatile solvent mixed with the regenerated cellulose and then or other inorganic basic agent. The saponifying 35 treated with a solvent to effect a binding of the particles. It may, however, be an inorganic bind- agents may be employed either in aqueous or in ing agent such as, for example, sodium silicate. alcoholic solutions. Preferably, we employ aque In some cases it is desirable to employ a binding , ous solutions of sodium hydroxide. agent such as a natural or synthetic thermoplas The sapom'fying solutions employed may be of a concentration of from 1 to 8% by weight de 40 tic or thermosetting resin in gum or powder form, and, after mixing the binding agent with the re pending upon the particular agent employed. generated cellulose, subjecting the mixture to a In the case of sodium hydroxide, we preferably shaping operation under the action of heat and employ aqueous solutions of a concentration of ' from 2 to 5% by weight. While the entire sa 45 pressure. A partially polymerized binding agent may also be employed, and after shaping the par poni?cation may be carried out employing either ponifying agent, the saponi?cation process may also be effected by the use of both an aqueous and an alcoholic solution of the vsaponifying agent. Thus, the saponi?cation may be initiated by em ploying an alcoholic solution of a saponifying agent and may be completed with an aqueous so- _ lution of the same or a different saponifying may be further polymerized in situ to form a ‘ shaped insulating material. Examples of suit able synthetic resins are phenol-formaldehyde products, cumaron resins, glyptal resins, poly merization products of vinyl compounds, and the like, while suitable natural resins are ob lophony, balsam, copaiba, dammar, elemi and mastic. The binding agent may be employed in agent. The ‘complete saponi?cation of the cel lulose ester material may also be carried out by 55 an amount ranging from 1 to 5% on the weight of the regenerated cellulose particles. The vola reversing these steps, i.v e. by ?rst employing an tile solvent employed may be acetone, diethyl aqueous solution of the saponifying agent and ether ethyl acetate, carbon tetrachloride, ethyl then completing the saponi?cation with an al alcoh\ 1, methyl alcohol, or the like. coholic solution of the same or a different agent. Between each saponi?cation step, the material 60 _ The cellular product of this invention may be may be washed with water if desired. The saponi?cation may be continued until the used as insulating material in any convenient manner. For insulating material in the form of board, a thin layer of the mix may be shaped cellulose ester comprising the cellular material is completely saponi?ed or it may be interrupted 65 between broad, ?at molding surfaces, while for insulating material of other shapes, suitably before complete saponi?cation has been effected, shaped molds may be employed. The mix may e. g. when the cellular material has .been saponi also be extruded in the desired shape through ?ed so that it loses about 25% of its weight. suitably shaped ori?ces by means of a screw Thus, the saponi?cation may be carried out for stuffer, or the like. After being suitably shaped from 1/,» to 5 hours and at a temperature of» from 70 the insulation material may be treated or coated 20 to 100° C. depending upon the concentration in any manner to render it water-proof or water of the saponifying agent, and the speed and de resistant. Such treatment may comprise sealing gree of saponi?cation desired. When saponi?ca the surface with a water-proo?ng material such tion has proceeded to the desired extent, it may as pitch or other water-insoluble or water-re be halted by washing the particles with water. sistant coating, or treating the formed insulat 3 2,898,001 ing material with formaldehyde or the like to render the regenerated cellulose water-resistant. when the boiling point is reached, the heat source _ is removed and the reaction mixture continues to boil due to the exothermic nature of the reaction. After about 3 to 4 minutes, the polymer which forms becomes insoluble in the solution and sep When used in a loose form the cellular particles may be blown into the air spaces or placed there in in any other convenient manner. In order further to illustrate our invention but without being limited thereto, the following ex amples are given. - Example I 200 parts by weight of cellulose acetate having arates. Polymerization ceases. The resin is washed with water, an excess of sodium carbon ate added, and the resin stirred to permit com plete neutralization of the sulfuric acid in the 10 resin. The resin is then washed several times with water with agitation, the water decanted or an acetyl value of 54.5% (calculated as acetic acid) is ground until it is of 20-30 mesh ?neness otherwise removed, and the resin dissolved in acetone, three parts acetone by weight to one and mixed thoroughly with 20 parts by weight of part resin by weight. ' butanol. The mixture is heated at 200° C. for 1 15' The mixture of resin and cellular regenerated minute under a pressure of 3000 lbs/sq. in. gauge. cellulose particles is heated in a mold at'l50° C. The pressure is released suddenly and the cellu for 30 minutes under a pressure of 2 pounds per lose acetate allowed to expand to ‘its maximum square inch, the elevated temperature causing the volume. The mass is broken up into small par acetone solvent to evaporate and the resin there ticles of about 0.5 to 1.0 cm. square. The ex in to polymerize further, rendering the resin in panded cellulose acetate particles are saponi?ed soluble in acetone and other organic solvents. for 3 hours with 1340 parts by weight of a 5% This polymerization cements the particles of re solution of sodium hydroxide maintained at 50° C. generated cellulose into a firm coherent mass. The regenerated cellulose particles are washed The density of this material is 0.16 and it has a free of alkali and dried at 100° C. for 2 hours. heat transfer coe?lclent of 0.2 cal./hour/cm.=/ 75 parts by weight of the dried, regenerated °C./cm. cellulose particles are mixed with 75 parts by weight of a 15% solution of cellulose acetate hav ing an acetyl value of 40%v in a 85/15 acetone/wa ter solvent. While our invention has been more particular ly described in connection with the use of cel lulose acetate in the preparation of our novel in The mixture is placed in a square 30 sulating material, other cellulose esters may also mold and maintained at 120° C. for 1/g hour. The ?rm cake obtained in this manner is main be employed. Examples of other cellulose esters are cellulose propionate and cellulose butyraig, tained at 100° C. to remove all of the residual mixed esters such as cellulose acetate-propionate and cellulose acetate-butyrate, and inorganic esters, such as cellulose nitrate, preferably of low nitrogen content. Where cellulose acetate is em ployed it may have an acetyl value of 40% to acetone. The product has a density of 0.16 and a heat transfer coe?lcient of 0.201 cal./hour/ cm."/°C./cm. A cork board of similar dimensions has a heat transfer coe?icient of 0.335, employ ing the same units. Example II Regenerated cellulose insulating material inv cake form is prepared in accordance with Exam ple I. 10 parts by weight of the material is treated at 150° C. for 45 minutes with 100 parts by weight of 40% commercial formaldehyde at a pressure of 50 lbs./sq. in. The material is dried at 100° C. for 12 hours to remove the remaining formaldehyde. The resulting product is mois 62.5% , determined 'as acetic acid. In order to increase the strength or to modify 40 the appearance or properties of the objects being molded or extruded, ?brous or other ?llers'may be incorporated therein. Examples of such ? brous ?llers are ?bers of cotton, ?ax, hemp, ramie, jute and natural silk, while examples of other ?lling materials are cork, sawdust, wood shav ings, clay, asbestos, etc., or mixtures of these. In addition, pigmentsmay be incorporated in the material or the material may be dyed to obtain color effects. Suitable ?re-retardants such as, ture-proofed. It has a density of 0.166 and a heat transfer coemcient of 0.238 cal./hour/ 50 for example, NaI-ICOa, NaaP04, SnCl: and MgSiOa may also be incorporated in the insulation ma cm.=/°C./cm. Example III terials to reduce any ?re hazard. It is to be understood'that the foregoing de 200 parts by weight of cellulose acetate having tailed description is merely given by way of illus an acetyl value of 54.5 (calculated as acetic acid) 55 tration and that many variations may be made is ground until it is of 20-30 mesh ?neness and therein without departing from the. spirit of our mixed thoroughly with 20 parts by weight of a invention. - 50%-50% mixture by volume of ethyl alcohol and Having described our invention, what we desire benzoi. The mix is treated as inExample I for ex to secure by Letters Patent is: pansion. The disintegrated pieces are saponi?ed 60 1. Process for the production of heat-insula in 2,000 parts by weight of 5% alcoholic potas tion material from a cellulose ester of cellular sium hydroxide solution at 76° C. for 1 hour. The - structure, which comprises saponifying discrete particles of regenerated cellulose are then particles of a cellulose ester of a cellular struc- " washed several times with water, given a soak ture to obtain a regenerated cellulose of cellular ing for 1 hour in 1 liter of 1% aqueous acetic 65 structure, mixing said regenerated cellulose with acid, washed acid free, and dried at 100° C. for 2 a solution of an adhesive binder in a volatile hours. solvent and subjecting the resulting mixture to 75 parts by weight of this material is mixed a shaping operation at elevated temperature. with 10 grams of a solution of partially poly 2. Process for the production of heat-insula merized phenol-formaldehyde resin, the resin so 70 tion material from cellulose acetate of cellular lution being prepared as follows: 2 parts by structure, which comprises saponifying‘ discrete weight of 40% formalin solution containing 1% ' particles of cellulose acetate of a cellular struc of its weight of sulfuric acid to act as a catalyst ture to obtain a regenerated cellulose of cellular is mixed with 1 part by weight of phenol. The structure, mixing said regenerated cellulose with mixture is heated to boiling under re?ux, and 75 a solution of an adhesive binder in a volatile 4 2,398,001 5. Process for the production of heat-insula solvent and subjecting the resulting mixture to a shaping operation at elevated temperature. tion material from a cellulose ester of cellular 3. Process for the production of heat-insula structure, which comprises saponitying discretel tion material from a cellulose ester of cellular particles of a cellulose ester of a cellular struc structure, which comprises .saponifying discrete ture to obtain a regenerated cellulose of cellular particles of a cellulose ester of a cellular struc ture to obtain a regenerated cellulose of cellular structure, mixing said regenerated cellulose with an adhesive binding agent comprising/a solution structure, mixing said regenerated cellulose with an adhesive binding agent comprising a solution of cellulose acetate in a volatile solvent and sub-' jecting the resulting mixture to a shaping opera of a partially polymerized phenol-formaldehyde 10 tion at elevated temperature. resin in a volatile solvent and subjecting the re sulting mixture to a shaping operation at ele vated temperature. 4. Process for the production of heat-insula 6. Process for the production of heat-insula tion material from cellulose acetate of cellular structure, which comprises saponifying discrete ' particles of cellulose acetate of a cellular struc tion material from cellulose acetate of I cellular 15 ture to obtain a regenerated cellulose of cellular structure, which comprises saponifying discrete structure, mixing said regenerated cellulose with particles of cellulose acetate of a cellular struc ture to obtain a regenerated cellulose of cellular an adhesive binding agent comprising a solution of cellulose acetate in a volatile solvent and sub? structure, mixing said regenerated cellulose with jecting the resulting mixture to a shaping opera ' '’ an adhesive binding agent comprising a solution 20 tion at elevated temperature. of a partially polymerized phenol-formaldehyde resin in a volatile solvent and subjecting the re CLIFFORD I. HANEYJ sulting mixture to a shaping operation at elevated MERVIN E. MARTIN. temperature.